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MyBuilder Tech Blog:
Managing Background Processes within Symfony
Dec 02, 2016 @ 11:19:47

Edd Mann has written up a tutorial for the MyBuilder.com Tech blog about managing background processes in a Symfony application with the help of Supervisor.

When a web application reaches a sufficiently large size, it can become infeasible to perform all actions required within a single web request/response life-cycle. You may find yourself wishing to for example - batch up and send queued emails at particular intervals, or process payments asynchronous to the point in-time the user made the initial request. In this post I would like to discuss our changing use of background processes (both time-dependent and continuous) due to increasing throughput demands.

He starts out with the first approach most applications take when needing to run automated, asynchronous processes - cron. Using it and a custom bundle they created for it, Edd shows how to directly integrate the cron timing of commands into the class attributes. However, after a while the system grew and it needed something a bit more powerful than cron, something that could correctly handle long running processes. Ultimately they decided on Supervisor, a processes manager and control system that makes managing these processes simpler. He talks about the transition they made from cron over to Supervisor (safely) and how they integrated the signaling functionality Supervisor allows into their application.

tagged: symfony background process manage cron supervisor tutorial bundle

Link: http://tech.mybuilder.com/managing-background-processes-within-symfony/

Zend Developer Zone:
Scheduling ElePHPants (DateTime math is HARD)
Nov 18, 2016 @ 12:49:38

On the Zend Developer Zone there's a new post talking about scheduling in applications ("scheduling elePHPants") including both library recommendations and advice about code reuse.

It was while I was creating the 100th or so cronjob to do some very similar to the other 99 that I thought, “Hey! Why not just put all this in a database and check it once a minute instead?” [...] It would be so much easier to deal with in PHP. Also, cron does not scale well at all either in performance or management.

The problem is that cron is an elegant solution for “Do this at that time” type of problems. Every solution I came up with was basically re-creating cron. That in itself isn’t a bad thing, but the logic involved in doing what cron does is mind-melting.

[...] Then it hit me, I am probably not the first person that has had this need. There have probably been other people who needed to implement “Do this at that time” within a PHP application. So I started looking around. What I found was encouraging.

The author then mentions several packages that he went through searching for the right solution to his problem, noting that while Laravel-based solutions seemed nice, they wouldn't work with his framework choice (Slim). He decided on the cron-expression package, finding it to be the best fit for the project's needs.

I had spent countless hours trying to create the solution myself. [...] I got so lost in solving the problem, I forgot to look to see if someone had already solved it. [...] After I finally came to my senses, I tweeted that out to remind myself to “Use the Source”.
tagged: schedule task cron experience package code reuse datetime

Link: https://devzone.zend.com/7418/scheduling-elephpants-datetime-math-is-hard/

SitePoint PHP Blog:
Framework-Agnostic PHP Cronjobs Made Easy with Crunz!
Aug 23, 2016 @ 13:36:59

The SitePoint PHP Blog has a new tutorial posted from author Reza Lavaryan showing you how to use the Crunz package to make cronjobs a bit simpler in a more framework-agnostic way.

In this article, we’re going to learn about a relatively new job scheduling library named Crunz. Crunz is a framework-agnostic library inspired by Laravel’s Task Scheduler, but improved in many ways. [...] Before getting started, you should have a firm grasp of cronjobs, so please read our in-depth walkthrough if you’re unfamiliar with how they work.

The tutorial then starts in on the code, getting the library installed and setting up a basic task example. The "task" files are sets of cron-formatted commands that are read and executed much like the cron daemon would on a Unix-based system. Example code for a task and command are included. They also talk about the "frequency" settings allowed by the library and the helper methods to make creating them simpler. The post also includes details about task lifetime, running conditions, configuration and parallelism (among other topics).

tagged: crunz library cronjob cron helper tutorial introduction

Link: https://www.sitepoint.com/framework-agnostic-php-cronjobs-made-easy-with-crunz/

SitePoint PHP Blog:
A Comprehensive Guide to Using Cronjobs
Mar 31, 2016 @ 12:18:47

If you've ever wanted to learn about cron jobs, how to set them up and what kind of functionality they provide then the SitePoint PHP blog has the post for you. In this comprehensive guide to cron you learn about these topics and more.

There are times when there’s a need for running a group of tasks automatically at certain times in the future. These tasks are usually administrative, but could be anything – from making database backups to downloading emails when everyone is asleep. [...] This article is an in-depth walkthrough of this program, and a reboot of this ancient, but still surprisingly relevant post.

They start by going through some of the basic terminology and syntax, where the cron files live and what a typical file format looks like. Also included are instructions on:

  • how to edit the cron correctly (crontab)
  • the structure of each cron entry
  • how to have it run at the time you want
  • editing another user's crontab
  • cron permissions
  • redirecting output

They also talk about executing PHP in a cron job, how to prevent overlaps with a "lock" file . There's also a mention of Anacron as a replacement for cron and a few helpful hints to help you debug when things go wrong.

tagged: cron cronjob tutorial comprehensive guide configuration execution

Link: http://www.sitepoint.com/a-comprehensive-crash-course-into-cronjobs/

SitePoint PHP Blog:
Drupal 8 Queue API – Powerful Manual and Cron Queueing
Dec 14, 2015 @ 11:54:38

On the SitePoint PHP blog Daniel Sipos has written up a tutorial spotlighting a powerful feature of Drupal 8, the latest major release of this popular project: the Queue API. Queueing in Drupal allows you to offload tasks to be handled outside of the current web request.

The Queue API in Drupal allows us to handle a number of tasks at a later stage. What this means is that we can place items into a queue which will run some time in the future and process each individual item at that point and at least once. Usually, this happens on CRON runs, and Drupal 8 allows for a quick set up for cronjob based queues. It doesn’t necessarily have to be CRON, however.

They use two examples to help illustrate how to use the queueing system: one that uses the cron-based approach and another that's more manually triggered. They start out with the theory behind it all, talking about the different pieces (objects/classes) and how they fit together to make the queueing system. With that out of the way the article starts in on the code and the "Node Publish" queue, defining its basic structure and hooking it in to the framework. It shows you how to create the cron worker to process the queue and how to build the manual worker to do the same but only when specifically called.

tagged: drupal8 queue manual cron process defer processing tutorial

Link: http://www.sitepoint.com/drupal-8-queue-api-powerful-manual-and-cron-queueing/

Leonid Mamchenkov:
Weird PHP error output bug
Dec 10, 2015 @ 10:41:06

In a post to his site Leonid Mamchenkov shares an interesting output bug he came across in his work developing cron jobs and how they handled his errors.

We came across this PHP bug at work today. But before you go and read it, let me show you a use case. See, if you can spot the problem. We had a cron job script which [ran a PHP script and echoed a string when complete].

[...] We use similar code snippets all over the place, and they work fine. This particular one was a new addition. So the cron job ran and “Updating products failed” part happened. Weird. The PHP script in question has plenty of logging in it, but nothing was logged.

After adding more and more logging to the process and PHP script, nothing obvious was standing out. Finally, they noticed that the filename was incorrect but normally that would cause an error in the PHP command line execution. The tricky part here was in how PHP handled its errors. Their error_log and display_errors settings were such that the PHP "missing file" error was being swallowed up and not displayed.

tagged: bug cron output error missing file errorlog displayerrors

Link: http://mamchenkov.net/wordpress/2015/12/10/weird-php-error-output-bug/

Sameer Borate:
Cron Expression Parser in PHP
Jul 21, 2015 @ 10:15:09

If you've ever worked with the "cron" tool on a unix-based system, you know that there's a special syntax that comes along with defining when the commands should run. It can be difficult to get this timing exactly right, especially if you're very picky about the execution time. In this post from Sameer Borate he shows you a PHP library that can help not only parse current cron configurations but also provides shortcuts for common timings (ex: "daily" or "weekly").

Working with cron scheduling can many times be a frustrating affair. Although setting a few cron jobs at one time can be easy, calculating cron dates in the future in code can get time consuming quickly. The PHP cron expression parser described here can parse a CRON expression, determine if it is due to run, calculate the next run date of the expression or calculate the previous run date of the expression. You can calculate dates far into the future or past by skipping n number of matching dates.

He includes some examples of putting the library to use to define a cron object based on an expression (either via a shortcut or an actual cron time expression). You can then check to see if the cron is "due" or perform some various operations about its run dates. This includes a formatted output of the previous run time, the next run time and the calculation of the next/previous run time based on a relative timestamp.

tagged: cron parser library example tutorial run due evaluation datetime

Link: http://www.codediesel.com/php/cron-expression-parser-in-php/

Matthew Weier O'Phinney:
Deployment with Zend Server (Part 2 of 8)
Aug 29, 2014 @ 11:55:04

Matthew Weier O'Phinney has posted the second part of his series with some tips around application deployment with Zend Server. In this latest post he shares his second tip related to recurring jobs.

This is the second in a series of eight posts detailing tips on deploying to Zend Server.The previous post in the series detailed getting started with zf-deploy to create ZPK packages to deploy to Zend Server. Today, I'm looking at how to created scheduled/recurring jobs using Zend Server's Job Queue; think of this as application-level cronjobs.

Instead of running the jobs as cron tasks (which may or may not be installed if there's multiple servers), he opts for a software-based approach. He walks you through the use of the Zend Server Job Queue to create a simple reoccurring execution to run a PHP script at a certain time. He includes some code examples with one showing just the scheduling of a job and the other showing how to detach previous jobs and add only the new ones that weren't scheduled before.

tagged: deployment zendserver tip series part2 cron reoccurring jobs

Link: http://mwop.net/blog/2014-08-28-zend-server-deployment-part-2.html

DevShed.com:
PHP: Best Methods for Running Scheduled Jobs
Jun 28, 2012 @ 11:01:49

On DevShed.com today there's a new article posted looking at methods for running scheduled jobs based on responses to this forum post.

I have a webpage form that requires a date and time to be submitted. When it's submitted I need the back-end to run a script at the time and date specified. Have you ever needed to do something like this?

Some recommendations already posted include:

  • The UNIX "at" command
  • Setting up a queue system to manage the processes (using something similar to Gearman
  • Setting up a cron job to handle the periodic execution of the script.
tagged: execute scheduled job cron queue at unix opinion

Link:

PHPBuilder.com:
My Automated PHP Scripts for Creating FTP Connections to a Remote Server
Jun 19, 2012 @ 10:41:57

PHPBuilder.com has posted a new tutorial about creating automated FTP scripts to pull down information from a remote server (using FTP streams).

In 2007 I began working on a website project for an investment company in my hometown of Cleveland, Ohio USA. The purpose of this website was to automatically download financial data of traded securities from two (2) remote Web servers. [...] Both of these PHP scripts were set up on the Web server's "crontab manager" to automatically run at a set time each business day.

Code is included showing how to connect to the remote service (via curl) with a "ftp" stream-based URL as the location. Also included is an example using a fopen call to the URL and inserting the resulting data into their tracking tables. The other script pulls the data out and adds a new record to a transactions table for the current day.

tagged: ftp tutorial connection transaction mysql cron automation

Link: